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Clear Cached Memory on Ubuntu

Terminal - Clear Cached Memory on Ubuntu
sudo sync && sudo echo 3 | sudo tee /proc/sys/vm/drop_caches
2012-03-17 08:27:58
User: StephenJudge
Functions: echo sudo sync tee
-1
Clear Cached Memory on Ubuntu

"That's it. Not much to see here. The first command writes any cache data that hasn't been written to the disk out to the disk. The second command tells the kernel to drop what's cached. Not much to it. This invalidates the write cache as well as the read cache, which is why we have the sync command first. Supposedly, it is possible to have some cached write data never make it to disk, so use it with caution, and NEVER do it on a production server. You could ... but why take the risk?

As long as you are running a post 2.6.16 kernel,..."

Source: http://ubuntuforums.org/showpost.php?p=3621283&postcount=1

Alternatives

There are 7 alternatives - vote for the best!

Terminal - Alternatives
sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
sync; echo 3 > /proc/sys/vm/drop_caches
sysctl -w vm.drop_caches=3
free && sync && echo 3 > /proc/sys/vm/drop_caches && free
echo 3 > /proc/sys/vm/drop_caches

Know a better way?

If you can do better, submit your command here.

What others think

Funny trick, but yes never use it on any prod machine. There can be so much set in cache between the two commands, that it looks like naked free fall.

Comment by makidoko 246 weeks and 4 days ago

drop_caches doesn't drop READ/WRITE-requests. only cached information.

SYNC as well as echoing into DROP_CACHES is non-destructive

Comment by Syntaxerror 105 weeks and 6 days ago

Your point of view

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